UMBRELLA - UM Boundary Layer Representation including land-atmosphere interactions
Lead Research Organisation:
University of Leeds
Department Name: School of Earth and Environment
Abstract
The atmospheric boundary layer (BL) is the layer of the atmosphere near the Earth's surface which is directly influenced by the surface. The BL plays a key role in the atmosphere - controlling the exchange of heat, moisture and other atmospheric constituents (both natural and anthropogenic) between the surface and the free troposphere. The boundary layer is also crucial in the initiation of convection and so impacts on the location and timing of convective rainfall. Turbulence is a key characteristic of the BL but is generally too small scale to be resolved in weather and climate models and so needs to be parametrised. With increased computational resources it is now feasible to run operation weather forecasts at km scales where convection can be resolved explicitly (though not necessarily well resolved). As we move towards sub-km scale the models will also begin to resolve large scale boundary structures. This regime where we partly resolve these key processes is known as the grey zone. Modelling the boundary layer in the grey zone requires re-evaluation and modification of the boundary layer parametrisation schemes and their coupling to convection (parametrised or explicit).
This project will firstly evaluate the currently available boundary layer schemes and their coupling to convection in the Met Office Unified Model (MetUM) at different resolutions across the grey zone as well as testing any new developments produced as part of this programme. Secondly it will study the coupling between surface heterogeneity, boundary layer structures and convection to understand the key role of heterogeneity. Previous studies largely focus on homogeneous case studies, despite the fact that most land is actually not flat and covers a variety of land use and surface conditions. Including surface heterogeneity will allow a more thorough evaluation of the current boundary layer schemes as well as providing a physical underpinning for more realistic parametrisations which are aware of the underlying variability in the surface characteristics.
The project will make use of the latest field observations from the upcoming Wescon field campaign as well as data from long term observational sites in the UK and US. We will also utilise the latest Meteosat third generation satellite observations to evaluate the model in the tropics. We will combine these observations with idealised large eddy simulations and more realistic simulations with the MetUM to study the behaviour of the boundary layer over the diurnal cycle at homogeneous sites and for heterogeneous regions (e.g. regions with variable surface temperature and moisture, or gentle topography).
This project will firstly evaluate the currently available boundary layer schemes and their coupling to convection in the Met Office Unified Model (MetUM) at different resolutions across the grey zone as well as testing any new developments produced as part of this programme. Secondly it will study the coupling between surface heterogeneity, boundary layer structures and convection to understand the key role of heterogeneity. Previous studies largely focus on homogeneous case studies, despite the fact that most land is actually not flat and covers a variety of land use and surface conditions. Including surface heterogeneity will allow a more thorough evaluation of the current boundary layer schemes as well as providing a physical underpinning for more realistic parametrisations which are aware of the underlying variability in the surface characteristics.
The project will make use of the latest field observations from the upcoming Wescon field campaign as well as data from long term observational sites in the UK and US. We will also utilise the latest Meteosat third generation satellite observations to evaluate the model in the tropics. We will combine these observations with idealised large eddy simulations and more realistic simulations with the MetUM to study the behaviour of the boundary layer over the diurnal cycle at homogeneous sites and for heterogeneous regions (e.g. regions with variable surface temperature and moisture, or gentle topography).
Publications
Charlton-Perez A
(2024)
Do AI models produce better weather forecasts than physics-based models? A quantitative evaluation case study of Storm Ciarán
in npj Climate and Atmospheric Science
| Description | Comparison of sub-km resolution forecasts with observations from the WESCON field campaign have demonstrated that at horizontal resolutions of 300m to 100m the Met Office Unified Model is capable of capturing boundary layer rolls that are not represented at the operational 1.5km resolution. These rolls compare well in terms of magnitude and size with aircraft observations, radar and satellite. Analysis of the model ensemble shows that mesoscale features such as sea breezes as well as orography play an important role in determining where the rolls occur and can impose predictability in the precise location of the rolls as well as influencing their strength. In the absence of such forcing the location of the rolls is stochastic. The impact of resolving the rolls on the sea breeze propagation is mixed - the sea breeze can propagate either faster or slower in different ensemble members. Further work is ongoing to understand the mechanisms of this. These boundary layer rolls play an important role in triggering convection and so accurately representing these impacts in turbulence parametrisations at coarser resolution is important. Evaluating the cost-benefits of running forecasts at sub km models is important in future decisions on how best to utilise increased computing power to improve weather forecasts. |
| Exploitation Route | We are working with the Met Office on this project to ensure the results feed through into model development of the turbulence and convection schemes in the MetUM and inform developments of operational sub-km resolution weather forecast models. |
| Sectors | Energy Environment |
| Description | This work is informing developments of sub-km weather forecast models at the Met Office. |
| First Year Of Impact | 2024 |
| Sector | Environment |
| Description | Met Office |
| Organisation | Meteorological Office UK |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | Research conducted as part of this collaboration has helped to constrain various parameters in the new COMORPH convection parametrisation scheme being developed for the Met Office weather and climate model (the MetUM) and is testing and validating the COMORPH scheme against observations, convection permitting simulations and large-eddy simulations. |
| Collaborator Contribution | This work has been conducted in close collaboration with the UK Met Office. Leeds is a founding member of the Met Office Academic Partnership and there are longstanding research collaborations between the atmospheric dynamics group in Leeds and various research groups at the Met Office. The partnership involves access to Met Office models and data for research and collaboration on joint strategic research topics and funding applications. The Met Office has led development of the code for the new COMORPH convection scheme and shared the code with academic partners involved in the project. |
| Impact | New COMORPH convection parametrisation scheme to included in upcoming versions of the MetUM. |